Laminated dry stencil



July 31, 1951 J. MORTON EIAL 2,552,676

LAMINATED DRY STENCIL Filed Jan. 6, 1948 2 Sheets-Sheet l k /2 V////////////////// /////////m FIG. 3

FIG. 4 /2 fag/WHY DI EUHEE u\\\ I /0 v fi/ JZ7H/ g ra/v 25 mzdw ATTORNEY July 31, 1951 J. MORTON ETAL 2,562,676

LAMINATED DRY STENCIL Fnd Jan. s, 1948 2 Shoots- Sheet 2 IN NTORE UHN HTUN ATTORNEY Patented July 31, 1951 LADIINATED DRY STENCIL John L. Morton, Endi cott, and Harry 0. George,

Vestal, N. Y., assignors to International Business Machines CorporatiomNew York, N. Y., a

corporation of New York Application January 6, 1948, Serial No. 798

1 Claim. 1

This invention relates to stencils and has among its objects to provide a stencil sheet which is more durable than dry-process stencils commonly used in duplicating machines. Other objects of the invention are to provide a stencil having qualities which render the stencil resistant to the softening influence of spirit, castor oil and other inks which normally affect the surfaces of stencils; to lengthen the useful period of general stencil use by providing a stencil surface which discourages deterioration and disintegration tending to the forming of unclear outlines in subsequent continued printing operations, and to provide a stencil capable of standing up against the destructive forces acting thereon as when a stencil is subjected to the repeated action of a rubber pressure roll of a check writing or like duplicating machine.

The tenuous character of the commonly used dry process stencil renders such a stencil not altogether suitable for use under conditions which require the employment of a rubber roll for effecting printing. For example, in a check writing machine which employs a rubber printing roll of 2.25 inches in diameter, sufilcient pressure is exerted upon the roll during a printing operation to produce a printing pattern of about 1.2 inches wide as measured transverse the roll. In accomplishing this, the cylindrical surface of the roll is flattened against the stencil to the desired width. The pressure exerted upon the stencil is of the order of 70 to 90 pounds per square inch and considerable frictional drag exists between the face of the rubber roll and the stencil as the rubber of the roll undergoes distortion during the application and release of the high loading required. Consequently, the stencil is considerably stressed during the printing operation and dry-process stencils do not stand up satisfactorily and soon become useless.

A dry process stencil is of the type of stencil commonly employed in duplicating machines wherein cylindrical ink-containing platens are rotated in contact with the sheets of paper being printed. Such a stencil comprises a porous sheet of very thin tissue paper usually less than .002 of an inch in thickness. A Japanese tissue paper, known by the name Yoshino, has been commonly used for this purpose. The porous paper is coated on one face with an impressible material which has wax-like characteristics and penetrates into the paper.

The dry process stencil is prepared for printing by displacing the impressible coating material at those places where the printing ink is intended to pass through the stencil. This displacement is. usually obtained by pressure exerted upon the tissue side of the stencil sheet, as by a type or stylus, and it is desirable to exert the pressure in such a manner that the porous base of the stencil is not punctured. This preparation for printing is called cutting" the stencil. A stencil of this type is so fragile as to have serious limitations for continued use and particularly in printing processes which require the application of heavy pressure such as is applied by the rubber roll in check writing machines.

For use in printing processes employing pressure rolls, an accepted practice has been to em-, ploy a variety of stencils which have to be moistened before cutting the stencil. The present invention provides a composite or laminated stencil which does not require wetting before being cut." This stencil consists of a sheet of stencil of the type commonly known as a dry process stencil and a sheet of a suitable tissue paper securely fastened together. The invention makes available all the desirable qualities and advantages of a dry process stencil in a stencil capable of withstanding the strenuous action of a rubber printing roll operating under relatively high pressure, as well as provides an improved stencil which is very satisfactory for general duplicating machine work.

In the drawings,

Fig. 1 illustrates the application of the invention to a stencil for ordinary duplicating machine work;

Fig. 2 illustrates on an enlarged scale an area of the stencil which has been cut for printing;

Fig. 3 is a section of the stencil showing its construction on an enlarged scale;

Fig. 4 is a section on line 4-l of Fig. 2 and illustrates the condition of the stencil when it has been cut preparatory to use;

Fig. 5 illustrates a stencil mounted in a card for use in a check writing machine; and

Fig. 6 schematically illustrates a process by which the stencil of the present invention may be fabricated.

Referring to the drawings, the stencil ill of the present invention consists of a sheet of dry process stencil H, such as is described hereinabove, attached to a sheet I2 of tissue paper in adhering relationship throughout their useful area. The securing together of the two sheets II and I! may be accomplished at the time the impressible coating is applied to a porous base sheet, or after the base sheet has been coated and is otherwise ready for cutting.

The tissue paper It which is attached to the invention. since 1034 separators used in making electrical condensers have been almost exclusivelycfthecelluloseorpaper type. Thistype of separator, which a well-known as condenser orcapacitor paper.consistsofathinsheet of specially fabricated paper or cellulose of extremely high purity from a'chemical point of view. Such capacitor papers are fabricated from selected cotton rag stock, although certain quantitles of other materials such as kapo lute or hemp may be added to the basic cotton rag pulp. Straight wood pulps, especially those of the sulphitcdprocessessuchaskraft,areespecially avoided. The thickness of the capacitor paper varies with the voltage rating of the capacitor structure and the type of electrolyte employed. hr example, the thickness varies on the average' from 0.003" to 0.008" in connection with capacitors rated from 6 volts to 800 volts, respectiv'ely. For use in the present invention, a thinner gauge of condenser paper is employed and it is therefore herein referred to as tissue. Capacitor tissue is a dense non-absorbent material and provides a strong and thin oil-proof sheet which is easily perforated by type-face when it is laminated with a dry process stencil. Capacitor tissue is resistant to abrasion and ink penetration and strengthens the stencil without materially increasing the caliper of the finished stencil. A suitable stren th ning paper should be closely formed and nonporous, have a calendered finish and be free from all foreign materials. We have found that capacitor tissues ranging in thickness from about .00025 to .00075 of an inch are well suited for attaining the results desired, it being understood that the particular thickness is dependent upon the intendeduse of the stencil, the pressure and character of the cutting devices which are employed to cutthe stencil, and the improved results desired as;

for example, for either check writing stencil cards or for ordinary multigraphing use. The capacitor tissue may be substantially colorless or neutral, but if desired, colored capacitor tissue may be employed to give a more readable stencil.

Stencils of the present invention mounted for use in a conventional duplicating machine and in a'check writing machine are illustrated, in Figs. 1 and 5, respectively. For attachment to a duplicating machine a narrow strip of stifl paper is having appropriate openings it is secured to the upper edge of the stencil II. For check writing use the stencil II is mounted between bonded sheets of stifi material which constitute a frame ing area of the stencil is exposed.

The stencil of the present invention may be produced during'the process in which the coat ing is being applied to the porous base sheet.

pressed together. This procedure is schematically illustrated in Pig. 6 in which the strip of the porous base sheet of tissue paper 11 is taken from a roll II and is passed over a transfer roll fl by which the proper amount of coating material is applied to one face of the porous sheet. As the coated strip of tissue paper il approaches the rolls Ii and II, the strengthening tissue if is brought into contact with it's coated face. The two sheets are laminated under the pressure of the rolls, then dried and rewound preliminarily to cutting to size and mounting or attachment to a stiff paper strip or frame, such as are illustrated in Figs. 1 and 5. The coating material maybeofthekindusuallyusedinproducingdry process stencils, such as a plasticized solution of nitrocellulose, or other suitable material.

Another process for producing the stencil of the present invention consists of pressing together a dry process stencil which has been prepared for ordinary use'against a sheet or web of capacitor tissue while subjecting the laminated sheets to low temperature and pressure. Heat sealing may be accomplished in this manner at various temperatures, depending upon the softening point of the material with which the previously prepared dry process stencil is coated which is usually below 210 I". The capacitor tissue is applied to the most heavily coated side of the porous base sheet and the required pressure may be applied by the use of heated platens or calender rolls.

Still another manner of producing a suitable bond between a coated base sheet and the capacitor tissue without affecting the working characteristics of the completed stencil consists of applying a suitable adhesive which will permit heat sealing at low pressures without upsetting the soft coating material. This may be applied by spraying the most heavily coated face of the dry process stencil, or the capacitor tissue, uniting the two sheets and applying pressure thereto. For a coating material comprising a nitrocellulose the adhesive may comprise polymeric polyvinyl acetates including mixtures of two or more such polymers in a suitable solvent such as a ketone, for instance acetone. The amount of adhesive required is relatively small and its effect on the working qualities of the stencil is negligible. Only sumcient pressure between the dry process stencil and the condenser tissue is required to cause adherence between them.

A suitable bond between a previously prepared stencil and the strengthening capacitor sheet may be obtained by spraying a solvent for the coating material upon the most heavily coated surface of the stencil sheet and the capacitor tissue, and then applying pressure to bond the two sheets together. When the coating material comprises a nitrocellulose, any of the common solvents therefor may be used, as, for exhaving a window lg through m e work- -l': ample, ketones, esters, alcohol ether, or combinations thereof.

Regardless of the manner in which the finished stencil of the present invention is produced, the character of the finished stencil is such that when it is cut for use the strengthening capacitor tissue It is perforated by the cutting type or other device by which the coating is impressed. As isusual in coating ordinary stencils, the

. coating is impressed sufficiently to provide for thepassage of ink through the stencil during a printing operation. The capacitor tissue is easily perforated when laminated on the face of a dry process stencil sheet. The results of the action of the cutting device is diagrammatically illustrated in Fig. 4 in which the cut edges 22 and 23 of the capacitor tissue are shown at opposite sides of the area 24 which has been compressed by the cutting type.

What is claimed is:

A laminated dry process stencil sheet, comprising a sheet of thin porous tissue paper coated on at least one face with an impressible material having wax-like characteristics which penetrates into the paper and which, when the stencil sheet is cut, is displaced to the extent of permitting a printing ink to pass through the stencil, a sheet of capacitor tissue paper having a thickness of about 0.00025 to about 0.00075 inch which is resistant to abrasion and ink penetration but which is adapted to be perforated when the stencil is cut, and an adhesive layer bond- 6 ing the coated side of the first named sheet to said second sheet and comprising plasticized nitrocellulose, said adhesive layer serving with the second named sheet to provide a protective layer which is durable under high pressure conditions in use.

JOHN L. MORTON.

" HARRY 0. GEORGE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

